1. Field of the Invention
In a general aspect, the present invention relates to an apparatus for molding a continuous element of foamed plastics.
The present invention relates, more particularly, to an apparatus for molding a continuous element of foamed plastics which finds a preferred, although not exclusive use, as a construction member in the building industry.
2. Background of the Invention
In the following description and the subsequent claims, the term: "continuous foamed plastic element" is used to indicate a foamed plastic section bar, e.g. made of foamed polystyrene, which leaves the molding apparatus as a single piece substantially free from joints or breaks and having indefinite length.
As is known, in the field of building construction in general, the use has long enjoyed success of foamed plastic construction elements, preferably made of foamed polystyrene, in the form of sheets or section bars of appropriate shape and size, having the function of thermal and acoustic insulating material.
According to the most widespread known technique, such as for example that described in Italian patent n. 1,051,111 filed by the same Applicant, the construction elements of the type considered are obtained by cutting in pieces of predetermined length a continuous element produced by means of molding apparatuses comprising a mold in which a molding seat is defined having a shape mating that of the continuous element to be produced.
In each molding cycle, a metered quantity of expandable plastic material in granules is fed into the above mentioned seat and subjected to expansion with a mutual welding of the granules through the action of heat, so as to form a new portion of the continuous element and obtain its simultaneous welding with an adjacent portion formed in a preceding molding cycle.
At the end of the molding and subsequent stabilization operations, the mold is opened and the continuous element incorporating the new portion is made to advance by a distance corresponding to the length of the molding seat, so as to arrange the latter for receiving other granules and initiating a new production cycle.
In this manner, a continuous foamed plastic element of indefinite length is obtained by means of successive molding operations, which element may be subsequently cut in portions of definite length that may be chosen at will.
Although substantially meeting the purpose, the molding apparatus of the prior art displays poor operating flexibility and, more specifically, does not allow an easy control of the shape, and in particular of the height, of the continuous foamed plastic element where required.
Thus, for example, each time it is desired to change the height of the element to confer improved mechanical strength thereto, the prior art proposes to change the height of the molding seat defined in the mold, by inserting spacers of adequate thickness into the cover each time as needed.
Consequently, there is not only the need to stop the molding operations for adapting the mold, but also the need to keep in storage a set of spacers of different lengths to perform the desired adjustment as required.
It goes without saying that in addition to an undesired capital locking-up, such an `adjustment` may not in fact allow the production of elements having heights different from that predefined by the thickness of the available spacers.
This technique, furthermore, is very difficult if not impossible to apply each time it is desired to adjust the height of any lateral projections present in the continuous element, such as for example in the case of the so-called floor elements, when it is desired to impart to these elements improved thermal and acoustic insulation characteristics.
The drawbacks mentioned above, furthermore, become even more stringent whenever the continuous foamed plastics element incorporates metal reinforcing members, as described, for example, in European Patent EP 0 459 924. In this case, in fact, it is necessary to cut the metal members upstream of the molding apparatus, to remove the element molded during the previous molding cycle from the molding seat, to insert again the metal members into the molding seat, to place appropriate spacers and to close the mold outlet with a stopper, before the molding operations may be started again.
This is clearly a cumbersome and time-consuming procedure that unfavorably affects the efficiency of the molding cycle, as well as producing a not negligible waste of material.